Wednesday, February 21, 2007

Climate models and disaster prophecies: new astrology

Cornelia Dean has an article in the New York Times. It is a review of the book "Useless Arithmetic" by Pilkey and Pilkey on the left. One of the main points is that the model sensitivity is a property of a model, not a property of reality. If this sensitivity is small and the results don't depend on small variations of the parameters, it doesn't mean that the model is accurate: the model may still be a very poor description of reality.

Daniel Sarewitz from Arizona State University says:

In a complex, imperfect world quantitative models feed the delusion that society can predict its way out of its environmental dilemmas. The corrosive result is that politics and science have become inextricably interwoven to the considerable detriment of both. This engaging, wise, and far-reaching book diagnoses the causes and costs of our quantitative hubris, and in so doing points the difficult way toward a more productive relationship among science, democracy, and the vexing challenges of environmental stewardship.

Roger Pielke Sr. believes many scientists, policy-makers, journalists and other commentators place too much confidence in climate model results. "The overselling of regional and global models as robust projections rather than as sensitivity simulations, adds to the existing politicisation of climate science and provides justifiable criticism of the [IPCC] assessment reports," he says.

Richard Lindzen says climate models vastly overestimate temperature changes resulting from increases in CO2. All other things being equal, Lindzen says a doubling of CO2 should result in a global mean warming of just 1ºC. "Alarming predictions all require that water vapour and clouds act so as to greatly amplify the impact of CO2," he (and fellow critics) say in a recent critique of the Stern Review published in World Economics. "But it is freely acknowledged, including by the IPCC, that water vapour and especially clouds are poorly modelled, while the underlying physics for determining their behaviour is missing or even unknown."